JP2005221798A - Automatic focusing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic focusing system for speeding up automatic focusing by moving a wobbling lens for wobbling in automatic focusing of a contrast system irrespectively of a vertical synchronous signal, and also speeding up the wobbling by acquiring focal point evaluation values without halting the wobbling lens. <P>SOLUTION: The CPU 14 of the automatic focusing system detects whether or not the system is in focus by displacing the wobbling lens WL of a photographing lens to the closest side and the infinity side, and acquiring and comparing a focal point evaluation value at each displacement point, or detects a focusing direction when the system is out of focus. Then, the wobbling lens WL is moved irrespectively of the vertical synchronous signal of a video signal, and the focal point evaluation values are acquired at many displacement points without halting the wobbling lens WL. Then, a focus or a focusing direction is detected on the basis of the focal point evaluation values acquired at a plurality of displacement points. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an autofocus system, and more particularly to an autofocus system that performs automatic focus adjustment by a contrast method based on a video signal.

  Autofocus (AF) employed in video cameras such as TV cameras detects the contrast of a captured image based on a video signal obtained by an image sensor, and controls the focus so that the contrast becomes maximum (maximum). A contrast method is common. The contrast of the captured image is quantitatively detected by, for example, an integrated value obtained by extracting a high frequency component from a video signal obtained by the image sensor and integrating the high frequency component signal for each field. The integrated value indicates the level of the contrast of the photographed image and the degree of focusing, and is referred to as a focus evaluation value in this specification.

  Further, a hill-climbing method is generally known as a method for controlling the focus so as to achieve focus based on the contrast of the captured image, that is, the focus evaluation value. In the hill-climbing method, by comparing the focus evaluation values at different focus positions when the focus is moved, the focus is moved in that direction while detecting the direction (focusing direction) in which the focus evaluation value increases, and the focus is moved. However, this is a control method in which the focus is stopped at a position where the focus evaluation value does not increase even if it is the focus position. In the hill-climbing method, in general, wobbling is performed for detecting the in-focus state and the moving direction of the focus for in-focus (in-focus direction). Wobbling is an operation that shifts the focus to the near side and the infinity side (minor), obtains focus evaluation values at each displacement point, and compares the focus evaluation values to determine the in-focus or in-focus direction. Detected.

By the way, as in Patent Document 1, the movement of the focus during wobbling is performed in synchronization with the vertical synchronization signal of the video signal, and the focus is used for sampling of the focus evaluation value (video signal sampling for obtaining the focus evaluation value). There is something to stop. According to this, wobbling can be performed efficiently in terms of time, and focusing and the focusing direction can be accurately detected, which is effective.
Japanese Patent No. 2084987

  However, when the wobbling displacement amount (amplitude) is increased as in the case of high aperture, movement time for a plurality of vertical synchronization signals (for a plurality of fields) may be required. In such a situation, if the focus is stopped at the time of sampling the focus evaluation value as described above, the focus evaluation value is sampled in the next field only after the focus movement is slightly delayed from the switching point of the video signal field. In some cases, a time loss of about one field may occur. For this reason, the time required for wobbling becomes longer than the extension of the time required for moving the focus, and there is a possibility that the time until focusing is increased.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an autofocus system capable of increasing the speed of AF by increasing the speed of wobbling.

  In order to achieve the above object, an autofocus system according to claim 1 is based on a focus-adjustable photographic lens that forms a subject image on an imaging surface of an imaging unit, and a video signal obtained by the imaging unit. Focus evaluation value detection means for detecting a focus evaluation value indicating contrast of captured images sequentially captured by the imaging means, and wobbling by shifting the focus position of the photographing lens by a predetermined amount toward the close side and the infinity side. A wobbling means to be performed, and a focus evaluation value for a captured image captured by the imaging means at the time of wobbling is acquired from the focus evaluation value detecting means, and the in-focus state or the in-focus state is acquired based on the acquired focus evaluation value A focus movement direction detection means for detecting the movement direction of the focus, and focusing based on the detection of the focus movement direction detection means. In the autofocus system including the focus control means for controlling the focus as described above, the wobbling means moves the focus of the photographing lens regardless of the vertical synchronization signal of the video signal indicating the switching of the photographed image, and the focus The moving direction detection unit sequentially acquires the focus evaluation value from the focus evaluation value detection unit during the wobbling, acquires a focus position when the focus evaluation value is acquired, and a plurality of positions of the acquired focus It is characterized in that the in-focus state or in-focus focus movement direction is detected based on the focus evaluation value data at.

  According to the present invention, the focus movement during wobbling is performed at an arbitrary timing, and the focus evaluation value at that time is also acquired without stopping the movement of the focus. Can be detected at high speed, and AF can be speeded up.

  According to a second aspect of the present invention, in the invention of the first aspect, the wobbling means performs the wobbling by moving a wobbling lens different from a focus lens for focus adjustment. Yes.

  According to a third aspect of the present invention, there is provided the autofocus system according to the first or second aspect of the invention, wherein the focus movement direction detecting means uses the focus evaluation value data at a plurality of focus positions acquired during the wobbling. And a function indicating the relationship between the focus position and the focus evaluation value is obtained, and based on the obtained function, the in-focus state or the focus moving direction in focus is detected.

  According to the autofocus system of the present invention, wobbling can be performed at high speed, and AF speed can be increased.

  Hereinafter, preferred embodiments of an autofocus system according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing the overall configuration of a lens system to which the present invention is applied. The lens system shown in the figure is a system used for a television camera for broadcasting, for example, and includes a photographing lens (optical system) and a control system.

  The photographing lens includes a focus lens (group) FL that moves in the optical axis direction for focus adjustment, a zoom lens (group) ZL that moves in the optical axis direction for zoom adjustment (focal length adjustment), and a light amount adjustment. An iris I that opens and closes, a wobbling lens (group) WL that moves in the optical axis direction for detecting a focus state (detection of the in-focus direction, etc.) during autofocusing, and the like are disposed. The schematic configuration of the photographic lens is shown in FIG. 2. As shown in FIG. 2, the focus lens FL, the zoom lens ZL, the iris I, the wobbling lens WL, in order from the previous stage (object side), FIG. A master lens (group) ML or the like not shown in FIG. As shown in FIG. 2, the zoom lens ZL includes a variable power lens (group) VL and a correction lens (group) CL, and these lenses VL and CL move in the optical axis direction with a predetermined positional relationship. By doing so, the focal length is changed without changing the focus position.

  The subject light incident on the photographic lens configured in this way is imaged on the imaging surface of the imaging element (not shown) of the camera body (camera head) equipped with the photographic lens, and after photoelectric conversion by the imaging element, the camera Predetermined signal processing is performed by the signal processing unit in the body. As a result, an image (captured image) captured by the image sensor via the imaging lens is obtained by the camera body as an image signal of a predetermined format (for example, NTSC system).

  As shown in FIG. 1, each lens FL, ZL, WL, and iris I is connected to a corresponding focusing motor FM, zooming motor ZM, wobbling motor WM, and iris motor IM. The lenses FL, ZL, and WL are driven in the optical axis direction by FM, ZM, WM, and IM, and the iris I is opened and closed. The motors FM, ZM, WM, and IM are drive signals supplied from the CPU 14 to the focus amplifier FA, the zoom amplifier ZA, the wobbling amplifier WA, and the iris amplifier IA via the D / A converter 16, respectively. It is controlled at a rotation speed according to the voltage value.

  An instruction signal indicating the position (target position) and speed (target speed) of the focus lens FL or zoom lens ZL to be set from a controller such as the focus demand 12 or the zoom demand 10 according to the operation of the operator is sent to the CPU 14. It is provided via a converter 13. The CPU 14 controls the rotational speeds of the motors FM and ZM by changing the values of the drive signals output to the amplifiers FA and ZA so that the focus lens FL and the zoom lens ZL have the target position or target speed. Controls the position and speed of the focus lens FL and zoom lens ZL. The CPU 14 is provided with a position signal indicating the rotation position of the focus motor FM as information on the current position of the focus lens FL from the focus potentiometer FP via the A / D converter 13 and the current position of the zoom lens ZL. As position information, a position signal indicating the rotation position of the zoom motor ZM is provided from the zoom pontometer ZP via the A / D converter 13. When the instruction signal for the focus lens FL or the zoom lens ZL designates the target position, the focus motor FM or the focus motor FM or the current position of the focus lens FL or the zoom lens ZL is sequentially compared. The rotational speed of the zoom motor ZM is controlled. As will be described later, the focus control can be switched between manual focus (MF) control and autofocus (AF) control. In the case of MF control, the focus control is applied from the focus demand 12 as described above. The focus lens FL is controlled on the basis of the instruction signal, and in the case of AF control, the focus lens FL is controlled on the basis of a focus evaluation value obtained from a focus evaluation value detection unit 26 described later in detail.

  For the iris I, generally, an instruction signal for instructing the position (aperture value) of the iris I to be set is given to the CPU 14 from the camera body, and the CPU 14 uses the iris I as information on the current position of the iris I as described above. The iris motor IM is controlled while detecting the rotational position of the motor IM with the iris potentiometer IP, and the iris I is controlled so that the aperture value specified by the instruction signal is obtained.

  On the other hand, the wobbling lens WL is not controlled based on an instruction signal from the outside, but is controlled by outputting a driving signal for wobbling during autofocus described later from the CPU 14 to the wobbling amb WA. . The wobbling motor WM is, for example, a pulse motor, and no potentiometer is provided for feeding back the position of the wobbling lens WL.

  Further, the focus evaluation value indicating the contrast of the video (captured image) captured by the image sensor of the camera body is given to the CPU 14 from the focus evaluation value detection unit 26 during the AF control. The focus evaluation value detection unit 26 mainly includes an A / D converter 18, a high-pass filter (HPF) 20, a gate circuit 22, and an addition circuit 24. The A / D converter 18 includes a signal from the camera body. A video signal (luminance signal) is input. From the video signal converted into a digital signal by the A / D converter 18, only a high frequency component is extracted by a high pass filter (HPF) 20, and then input to the gate circuit 22. Then, the gate circuit 22 extracts a signal only in a predetermined AF area (for example, a rectangular area at the center of the screen) set in the photographing range (screen) by the gate circuit 22. FIG. 3 shows an example of the range of the AF area in the screen. The AF area shown in FIG. 3 is rectangular and has a horizontal width of about 1/3 of the horizontal width and vertical width of the screen. It has a vertical width. The video signal is directly given to the gate circuit 22, and the signal range corresponding to the AF area in each field is specified by referring to the synchronization signal of the video signal.

  The signal of the high frequency component in the AF area extracted by the gate circuit 22 is integrated for each field by the adding circuit 24, and the integrated value is given to the CPU 14 as a focus evaluation value. The CPU 14 executes AF control described below based on the focus evaluation value provided from the focus evaluation value detection unit 26 in this way. The method for detecting the focus evaluation value from the video signal is not limited to the above case. In addition, the focus evaluation value detection unit 26 is mounted on, for example, a lens apparatus that includes a photographing lens, a CPU 14, and motors FM, ZM, WM, IM, and the like.

  Next, AF control will be described. An apparatus that constitutes the lens system, for example, the focus demand 12 or the case part of the lens apparatus, is provided with an auto-return AF switch S1, and each time the AF switch S1 is turned on, an MF mode and an AF mode are provided. And can be switched. When the MF mode is selected by the AF switch S1, the focus lens FL is controlled by the MF control as described above in accordance with the instruction signal given from the focus demand 12.

  When the AF mode is selected, AF control by the contrast method is executed. The outline of AF control will be described. At the time of AF control, the focus evaluation value indicating the contrast of the captured images (images of each field) sequentially captured by the image sensor of the camera body via the imaging lens is the focus evaluation as described above. It is detected by the value detector 26. On the other hand, the CPU 14 outputs a drive signal to the wobbling amplifier WA while the focus lens FL is stopped to displace (vibrate) the wobbling lens WL back and forth in the optical axis direction from the reference position. That is, wobbling is performed. As a result, the focus (focus position) changes between the close side and the infinity side. At this time, the CPU 14 acquires a focus evaluation value at each displacement point of the wobbling lens WL from the focus evaluation value detection unit 26 as will be described in detail later. Then, based on the focus evaluation value at each displacement point, it is in focus (whether it is in focus or not), or the focus moving direction (in-focus direction), that is, focus evaluation. Detect the direction in which the value increases. In the following description, detection of in-focus is referred to as in-focus detection, and detection of a focus moving direction that is in focus is referred to as in-focus direction detection. In addition, the detection result of in-focus or in-focus direction by the wobbling is in focus with respect to the position where the focus lens FL is stopped during wobbling in a state where the wobbling lens WL is set to the reference position. Or, it indicates the moving direction of the focus (focus lens FL) that is in focus when not in focus.

  When the CPU 14 detects the in-focus or in-focus direction by wobbling, the CPU 14 controls the focus lens FL based on the detection result. FIG. 4 shows the focus position (focus position) on the horizontal axis and the focus evaluation value on the vertical axis, and each focus position on the assumption that the subject condition is constant and the focus is moved from the closest end to the infinity end. 2 shows an example of a graph of focus evaluation values detected by. When the focus lens FL is stopped at a position where the focus evaluation value reaches a peak as indicated by point a in the figure, it is detected that the lens is in focus by wobbling. In this case, the focus lens FL is stopped at the current position without moving.

  On the other hand, when the focus lens FL is stopped at a position where the focus evaluation value does not reach a peak, such as point b or point c in FIG. In the case of point b, it is detected that the in-focus direction is on the infinity side, and the CPU 14 moves the focus lens FL to the infinity side by a predetermined amount by the drive signal output to the focus amplifier FA and stops it. Conversely, in the case of point c, it is detected that the in-focus direction is the close side, and the CPU 14 moves the focus lens FL to the close side by a predetermined amount and stops it.

  Detection of in-focus or in-focus direction by wobbling as described above and control of the focus lens FL in accordance with the detection result are repeatedly performed by the CPU 14, whereby the focus lens FL moves in the in-focus direction and is in focus. Stop at position. Even when the focus lens FL is stopped at the in-focus position, wobbling is repeatedly performed every predetermined time, so if the in-focus position changes due to a change in the state of the subject, a new in-focus position The focus lens FL moves and stops.

  When the focus lens FL is set to the in-focus position, it may be detected that the in-focus position has been changed not by wobbling but by other processing. For example, when focus is detected by wobbling and the focus lens FL is stopped at that position, wobbling is stopped and focus evaluation values are sequentially acquired from the focus evaluation value detector 26. Then, it is monitored whether or not a change of a certain value or more has occurred in the focus evaluation value, and when a change of a certain value or more is detected, it is determined that a change has occurred in the photographed image, and focusing or focusing by the wobbling is performed. The detection of the focus direction and the control of the focus lens FL are resumed. As a result, when the focus position changes, the focus lens FL moves to a new focus position.

  Also, instead of so-called continuous AF in which AF control is continuously performed after focusing as in the AF control described above, AF control is stopped when the focus is switched once to the AF mode, for example, MF mode. One-shot AF control that shifts to may be used.

  Further, the amount of movement of the focus lens FL per time when the in-focus direction is detected as infinity or close side by wobbling may be constant or may be changed based on the focus evaluation value at the time of wobbling. May be. In addition, when changing the amount of movement of the focus lens FL per time, either the moving speed or the moving time may be changed, or both may be changed.

  Next, the processing of the CPU 14 during wobbling will be described in detail. FIG. 5A shows the time axis in the horizontal direction, and the time axis is divided into fields of the video signal (field period is 1 / 60≈16.7 ms). As shown in FIG. 5B, when the wobbling is performed, the CPU 14 starts the movement of the wobbling lens WL regardless of the arbitrary timing, that is, the vertical synchronization signal, and the wobbling lens WL is displaced from the reference position to the closest side maximum. For example, it is moved to a point in about 2 fields (1/30 s). Next, without stopping the wobbling lens WL at the closest maximum displacement point, the moving direction is reversed from the close side to the infinity side, and for example, the maximum displacement at the infinity side in about 4 fields time (1/15 s). Move to a point. Further, without stopping the wobbling lens WL at the maximum displacement point on the infinity side, the moving direction is reversed from the infinity side to the close side, and moved to the reference position, for example, for a time of about 2 fields (1/30 s). Stop. It is assumed that the displacement amount from the reference position to the closest maximum displacement point is equal to the displacement amount from the reference position to the infinity maximum displacement point. Further, these displacement amounts may be changed to appropriate amounts according to the focal length and aperture value of the photographing lens (for example, the displacement amount is increased at the time of high aperture).

  In addition, from the start to the end of wobbling as described above, the CPU 14 acquires a focus evaluation value for each field from the focus evaluation value detection unit 26. That is, the focus evaluation value detected by sampling the video signal in the range corresponding to the AF area among the video signals of each field is acquired for each field without stopping the wobbling lens WL. Further, the position of the wobbling lens WL when the video signal in the range corresponding to the AF area is sampled is stored in association with the focus evaluation value detected by the sampling of the video signal. The sampling of the video signal in the range necessary for detecting the focus evaluation value, that is, the sampling of the video signal in the range corresponding to the AF area is hereinafter referred to as focus evaluation value sampling. Further, the wobbling lens WL moves while sampling the focus evaluation value, but the position of the wobbling lens WL stored in association with the focus evaluation value is, for example, sampling the focus evaluation value. The position of the wobbling lens WL at a predetermined point in the sampling period, such as the start point, end point, or intermediate point of the period. Further, in order to acquire the focus evaluation value when the wobbling lens WL is at the reference position, the focus evaluation value may be acquired before the start of the movement of the wobbling lens WL as shown in FIG. Alternatively, the focus evaluation value may be acquired after the movement of the wobbling lens WL is completed. However, it is not always necessary to acquire the focus evaluation value when the wobbling lens WL is at the reference position.

  Subsequently, the CPU 14 uses the focus evaluation value at each displacement point and the position of the wobbling lens WL acquired during wobbling as described above as a pair of data (referred to as focus evaluation value data), and multipoint focus evaluation value data. Is used to detect the in-focus or in-focus direction.

  There are several methods for detecting the in-focus or in-focus direction using multi-point focus evaluation value data. For example, a wobbling lens using multi-point focus evaluation value data and Lagrange's interpolation polynomial is used. It is possible to obtain a relational expression y = P (x) between the WL position x and the focus evaluation value y and detect the in-focus or in-focus direction from the relational expression. It should be noted that the relational expression y = P (x) indicating the relationship between the position x of the wobbling lens WL and the focus evaluation value y may be obtained by another function such as a spline function instead of the Lagrange interpolation polynomial. Good.

但し、

そして、上式Ｐ（ｘ）を１階微分した式Ｐ′（ｘ）も容易に求められ、その微分式Ｐ′（ｘ）のｘの値としてワブリングレンズＷＬの基準位置の値（０とする）を代入したときのＰ′（０）の値を求めることによって、合焦又は合焦方向を検出することができる。例えば、無限遠方向を正の方向とすると、Ｐ′（０）が０（又は０とみなせる程小さい値）であれば合焦していると判断することができ、合焦と判断されない場合であって、Ｐ′（０）が正であれば合焦方向を無限遠側、Ｐ′（０）が負であれば合焦方向を至近側と判断することができる。 The method using Lagrange's interpolation polynomial is as follows. A value indicating the position of the wobbling lens WL is an x coordinate, a focus evaluation value is a y coordinate, and focus evaluation value data at each displacement point acquired at the time of wobbling is a point (x ₀ , y ₀ ) on the xy coordinate, It is assumed that (x ₁ , y ₁ ), (x ₂ , y ₂ ), ..., (x _N , y _N ). At this time, the equation P (x) of the curve passing through each point of the focus evaluation value data is expressed as follows by Lagrange's interpolation polynomial.

However,

A formula P ′ (x) obtained by first-order differentiation of the above formula P (x) is also easily obtained, and the value of the reference position of the wobbling lens WL (0 and By determining the value of P ′ (0) when substituting (Yes), the in-focus or in-focus direction can be detected. For example, assuming that the direction at infinity is a positive direction, if P ′ (0) is 0 (or a value that is small enough to be regarded as 0), it can be determined that the focus is achieved, and the focus is not determined. If P ′ (0) is positive, the in-focus direction can be determined as infinity, and if P ′ (0) is negative, the in-focus direction can be determined as the closest side.

  Another method using Lagrangian interpolation polynomials can be performed as follows. In contrast to the differential expression P ′ (x) obtained by the Lagrangian interpolation polynomial, the focus evaluation value has a peak when x satisfies the condition of P ′ (x) = 0, and x indicates the in-focus position. . Therefore, x satisfying the condition of the differential expression P ′ (x) = 0 is obtained, and if the value of x matches the value indicating the reference position of the wobbling lens WL (or it can be regarded as a value indicating the reference position). If it is close, it can be determined to be in focus. On the other hand, if it is not determined to be in focus and the value of x is a value indicating a position on the infinity side from the reference position, the in-focus direction can be determined to be the infinity side, and closer to the reference position. If the value indicates the position, the in-focus direction can be determined as the closest side.

  As described above, it is possible to detect the in-focus or in-focus direction by wobbling, and the focus lens FL moves in the in-focus direction by controlling the focus lens FL as described above according to the detection result. Stop at the focal position.

  If the stop position of the focus lens FL during wobbling is close to the in-focus position, x satisfying the condition of the differential expression P ′ (x) = 0 with respect to the differential expression P ′ (x) is accurately matched. Since it is considered to indicate the focal position, the position of the focus lens FL that is equal to the focus position when the wobbling lens WL is set to the position of x is obtained, and the focus lens FL is moved directly to that position. Also good.

  In the above embodiment, the wobbling lens WL is moved in the entire range between the predetermined close-side maximum displacement point and the infinity-side maximum displacement point, but the wobbling lens WL is moved. When the focus or the focus direction can be detected from the focus evaluation value data obtained halfway, it is not always necessary to move the wobbling lens WL over the entire range.

  In the above embodiment, the wobbling lens WL is moved in a triangular wave shape as shown in FIG. 5B. However, for example, a sine drive having a sine wave shape may be used. The sine drive is more advantageous for speeding up wobbling.

  Subsequently, as in the above embodiment, in the case where wobbling is performed regardless of the vertical synchronization signal of the video signal and the focus or the in-focus direction is detected based on the focus evaluation values acquired at a number of displacement points. The effect of will be described. FIG. 6 is a diagram showing conventional wobbling control. In FIG. 6A, like FIG. 5A, the horizontal axis represents the time axis, and the time axis is divided for each field of the video signal. Conventionally, wobbling control is performed as follows. As shown in FIG. 5B, the wobbling lens WL is stopped at the reference position until the time of about one field has elapsed since the detection of the vertical synchronizing signal of the video signal before starting the movement of the wobbling lens WL. Now, a focus evaluation value obtained from the video signal sampled during that time is acquired. Next, the movement of the wobbling lens WL is started in synchronization with the vertical synchronizing signal, and the wobbling lens WL is moved to the closest maximum displacement point while the time of about 2 fields elapses. Thereafter, the wobbling lens WL is stopped at the closest maximum displacement point until the time of about one field has elapsed until the vertical synchronization signal is detected twice. Then, a focus evaluation value obtained from the video signal sampled during that time is acquired. Next, the movement of the wobbling lens WL is started in synchronization with the vertical synchronizing signal, and the wobbling lens WL is moved from the closest maximum displacement point to the infinity maximum displacement point during the time of about 4 fields. Let Thereafter, the wobbling lens WL is stopped at the maximum displacement point on the infinity side until the time of about one field has elapsed until the vertical synchronization signal is detected twice. Then, a focus evaluation value obtained from the video signal sampled during that time is acquired. Subsequently, the movement of the wobbling lens WL is started in synchronization with the vertical synchronizing signal, and the wobbling lens WL is moved to the reference position while the time of about 2 fields elapses.

  According to this conventional wobbling control, the wobbling lens WL is stopped for a time corresponding to one field in order to detect one focus evaluation value, so that compared with the above-described embodiment (the present invention). Takes time. Further, even if the time required for the movement of the wobbling lens WL is the same as that in the above embodiment (the present invention), conventionally, depending on the movement time of the wobbling lens WL to each displacement point, After moving to each displacement point, there may be a time lapse until a video signal of the next field in which the focus evaluation value can be sampled is provided, which requires more time than the above embodiment (the present invention). In some cases. Therefore, the above embodiment (the present invention) has an advantage that the speed of wobbling can be increased. In the above embodiment (the present invention), since the wobbling lens WL is not stopped when the focus evaluation value is acquired, the focus evaluation value is acquired compared with the case where the wobbling lens WL is stopped and the focus evaluation value is acquired. Although the accuracy of the focus evaluation value is lowered, since the focus and the focus direction are determined from a large number of focus evaluation value data acquired during wobbling, the reliability of the determination can be improved. In particular, when the AF area is small in the vertical direction, it has the same effect as the shutter, and even if the focus evaluation value is acquired while moving the wobbling lens WL, the relationship between the focus position and the focus evaluation value is highly accurate. The determination of in-focus and in-focus direction so that it can be detected is sufficiently reliable. Further, in the above embodiment (the present invention), multiple points of focus evaluation value data are acquired at the time of wobbling, and wobbling is performed when an average value of a plurality of focus evaluation values is calculated for flicker prevention or the like. There is also an advantage that the calculation can be performed at high speed without increasing the time.

  As described above, in the above embodiment, wobbling is performed by the wobbling lens WL. However, the wobbling may be performed by vibrating the focus lens FL without using the wobbling lens. Can be applied.

  The present invention can be applied not only to a television camera but also to a camera that uses contrast-type autofocus.

FIG. 1 is a block diagram showing the overall configuration of a lens system to which the present invention is applied. FIG. 2 is a configuration diagram showing a schematic configuration of the photographing lens. FIG. 3 is a diagram showing an example of the AF area in the screen. FIG. 4 is an explanatory diagram used for explaining the control of AF. FIG. 5 is an explanatory diagram used for explaining control of wobbling. FIG. 6 is an explanatory diagram used for explaining the control of the conventional wobbling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 ... Focus demand, 14 ... CPU, 13 ... A / D converter, FP ... Focus potentiometer, 18 ... A / D converter, 20 ... High pass filter, 22 ... Gate circuit, 24 ... Adder circuit, 26 ... Focus evaluation Value detection unit, S1 AF switch, FL focus lens, ZL zoom lens, I iris, WL wobbling lens, FM focus motor, WM wobbling motor

Claims (3)

A focus-adjustable photographic lens that forms a subject image on the imaging surface of the imaging means, and a focus evaluation value that indicates the contrast of the photographic images sequentially taken by the imaging means based on the video signal obtained by the imaging means. Focus evaluation value detection means for detecting, wobbling means for wobbling by shifting the focus position of the photographing lens by a predetermined amount toward the close side and the infinity side, and a photographed image captured by the imaging means during the wobbling A focus evaluation value with respect to the focus evaluation value detection means, and a focus movement direction detection means for detecting a focus moving direction that is in focus or in focus based on the acquired focus evaluation value, and the focus movement An autofocuser comprising focus control means for controlling the focus so as to be in focus based on detection by the direction detection means In the system,
The wobbling means moves the focus of the photographing lens irrespective of the vertical synchronization signal of the video signal indicating the switching of the photographed image, and the focus movement direction detection means detects the focus evaluation value detection means during the wobbling. The focus evaluation value is sequentially acquired, the focus position at the time of acquiring the focus evaluation value is acquired, and the focus is obtained based on the focus evaluation value data at the plurality of positions of the focus. An autofocus system characterized by detecting a moving direction of the focus.   2. The autofocus system according to claim 1, wherein the wobbling means performs the wobbling by moving a wobbling lens different from a focus lens for focus adjustment.   The focus movement direction detection means obtains a function indicating the relationship between the focus position and the focus evaluation value using the data of the focus evaluation values at a plurality of positions of the focus acquired during the wobbling, and obtains the function 3. The autofocus system according to claim 1, wherein a focus moving direction or a focus moving direction in focus is detected based on a function.

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